The process of manufacturing stone blocks, commercially known as Brentonstone, described in document U.S. Pat. No. 4,698,010, is well known. By means of said process, a mass of inorganic fillers of a known particle size, pigments or dyes, an organic binder and additives is formed, in amounts suitable to make the formation of said material possible by means of the simultaneous action of vacuum compression and vibration.
There are currently several patent documents, such as for example, US 2006/0162618 A1, ES 2166947 T3, WO 2005/111126 A1, WO 99/23045 A1, which describe processes for obtaining slabs from stone materials, generally granulated materials which are agglomerated in most cases by means of a binder that is usually a polyester, epoxy or acrylic type thermoset organic resin and, in any case, a petrochemical polymer, with an amount of synthetic diluents such as styrene, toluene, xylene, etc., and other additives, as the case may be.
Document ES 2187313 A1, by the authors of the present application, describes a method for manufacturing artificial stone slabs that can be applied to decoration from a mixture of ground materials with different particle sizes of silicas, glasses, granites, ferro-silicon quartz, marble or other similar materials and 7% to 14% by weight of polyester resin, as well as other additives, such as a dye for example, as well as a catalyst, a coupling agent and accelerant which act on the resin. Also by the same authors, document WO 2005/014256 A1 describes a material with appearance of natural stone formed from a mixture of natural stone materials and 6% to 30% by weight of polyester resin, to which an antimicrobial material is added to prevent the proliferation of bacteria or microbes on the surface, the obtained material being suitable for domestic use, specifically in bathroom and kitchen counters. Likewise, in document WO 2006/134179 A2, slabs of artificial stone and polymerizable resin (4% to 15% polyester) having a veined effect are obtained by using the vacuum vibro-compression technique like in the two documents mentioned above.
Document EP 2011632 A2, also by the authors of the present application, describes a process for manufacturing slabs with mixtures similar to those described in the previous documents and 5% to 15% polyester resin, characterized in that the curing process for obtaining the hardening of said resin is carried out by means of microwave irradiation and calcium carbonate or sulfate are added to the resin as catalysts to facilitate said process.
In recent years, the consumption of stone agglomerates for their use as kitchen counters, bathroom counters or as a work surface in general, and also for their use as flooring or wall cladding, has considerably increased, being a very common product so the production level and, therefore, the consumption of resin, have greatly increased.
As a result, an important part of research in this field has been dedicated to searching for components which come from renewable and/or recycled raw materials that are more environmentally friendly and make the overall process cleaner and more efficient, and at the same time allow manufacturing a material with excellent mechanical and aesthetic features.
Thus, raw materials from stone waste from construction, recycled glass, industrial waste, etc., are described in various patent documents, such as for example document KR 20020051443, which describes the manufacture of construction materials, such as bricks, blocks, tiles, etc, using limestone and waste materials generally from construction. Document ES 2249163 A1 describes a system of using disposable alabaster waste, using said waste in a container where a settling process is carried out by vibrating said waste, and the polyester resin is subsequently poured in, with which the combination is mixed under vacuum. The resin used is preferably polyester resin mixed with alabaster or dolomite powder.
Other documents using waste materials are, for example, WO 00/44686 A1 which uses waste glass for manufacturing artificial stone, and ES 2121529 A1 which uses ground recycled glass for manufacturing cement agglomerates. Document WO 89/11457 A1 also uses a synthetic resin with a mixture of recycled glass and new glass, among other materials, to obtain artificial stone with a natural appearance.
Document US 2006/0051598 A1 describes a slab or block manufactured from an agglomerate material comprising fragments, in the form of powder, grit or the like, and pure silicon tablets previously used in the electronic industry as wafer supporting microchips and silicon tablets of printed circuits, mixing all the components with an agglutinating agent and a dye for obtaining the desired product.
There are also documents in the state of the art which describe the use of resins that are less aggressive with the environment, or in which the reactive solvent which usually contains said resin is removed. As in the case of patent application WO 2007/138529 A2, which describes the manufacture of a stone agglomerate from the use of a polyester resin free of reactive diluents (without styrene) and formed by the reaction between an epoxidized triglyceride and at least one carboxylic anhydride and in which the necessary triglycerides can be obtained starting from vegetable or animal fats. With this method, which is already known in other sectors as shown in documents U.S. Pat. No. 3,296,202 and DE19627165, a resin is obtained which is not a polyester resin per se, but rather a partially epoxidized system. Despite the fact that the physico-mechancial properties of these resins are very satisfactory, the main problem with their use is that it would be necessary to have the process infrastructure suitable epoxidizing the fatty acids and, with it, obtaining the resin. Furthermore, the catalytic system needed for polymerizing this resin is completely different from the systems which are used today, which would make it necessary to make substantial mechanical changes in the already implemented processes, with the economic investment this involves, and eliminating the possibility of being able to reuse current systems.
Instead of removing the styrene which is used with the resin, another possibility would be to obtain said resin from elements of a plant origin. Thus, document U.S. Pat. No. 6,222,005 B1 describes a process for preparing a polyester resin by means of two steps: a) reacting a carboxylic acid, containing at least two carboxyl groups, or its corresponding anhydride containing one ethylenic unsaturation with a saturated, monohydric alcohol having a boiling point of less than 150° C., in an amount sufficient to obtain the half ester, and b) reacting the half ester obtained in (a) with a polyol in the presence of an oil containing one unsaturation or the corresponding fatty acid, which can be present by up to 45%. Said oil is selected from the group of castor, peanut, olive, cottonseed, soybean or rape seed oil. The use of said unsaturated oils allows reducing the use of petroleum byproducts. The resin thus obtained is used in the manufacture of composites for agricultural, marine and transport equipment.
Therefore, there is still a need to develop polyester resins derived from petroleum byproducts, with optimal properties for manufacturing quartz agglomerates in which the glycols of a petrochemical origin are partially substituted with glycols obtained from a plant origin, the catalytic system of which is the one typically used and does not require mechanical changes in the process and obtains a quartz agglomerate with features similar to or better than those traditionally obtained.
Thus, the present invention describes a panel or slab formed from a polyester resin which has been partially replaced with polyols of a plant origin, such as from corn, for example. Furthermore, it has surprisingly been found that said resin containing polyols of a plant origin is perfectly suitable for the process of manufacturing said panel or slab, partially or entirely substituting the conventional inorganic aggregates with others from different industrial processes or other uses, such as ground glass from recycled bottles, flat glass from the glass manufacturing industry, porcelain material from waste processes in processes for manufacturing porcelain, etc. Thus, a panel or slab with resin of a plant origin, and furthermore with a high raw material content of renewable and/or recycled raw materials, and which is therefore environmentally friendly, is obtained.